Pollen

Thanks very much, all, for your help with pollen. I remember learning
about sperm nuclei, but my textbooks and instructors were always vague
about exactly what these are. It always seemed odd to me that they could
just be "nuclei", yet motile, or on the other hand cells, presumably
with walls and plasma membranes, yet formed internally to the pollen
"cell". Thanks for clearing up part of that story.